Buffer assembly for firearm reciprocating bolt

ABSTRACT

A buffer assembly for a firearm has a tubular receiver extension. A damper assembly is positioned within the receiver extension adjacent the receiver extension rear end, and a spring is positioned within the receiver extension with the rear end of the spring surrounding the damper assembly. A buffer is positioned within the receiver extension at the opposite end of the spring from the damper assembly. The receiver extension has a liner that surrounds the spring creating a layer between the spring and the receiver extension. The liner may be a friction reducing material such as a polymer material.

FIELD OF THE INVENTION

The present invention relates to the action of a firearm. In particular,the present invention relates to a buffer assembly used in conjunctionwith a reciprocating bolt firearm.

BACKGROUND OF THE INVENTION

Existing reciprocating bolt firearms, including carbines and rifles,such as the AR15/M16 among others, employ a buffer assembly to reducethe effect of recoil on the operator and as part of the firing cycle ofthe firearm. The buffer assembly typically includes a buffer tube, abuffer spring and a buffer. However, existing buffer assemblies sufferfrom a number of deficiencies. For example, existing assemblies areheavy, noisy, operate in course or rough manner that distracts theoperator, require significant maintenance, and are not easily adjustedto meet individual requirements.

BRIEF DESCRIPTION OF THE FIGURES

Advantages of the invention will become apparent upon reading thefollowing detailed description and upon reference to the drawings.

FIG. 1 is an exploded isometric view of a buffer assembly in accordancewith existing firearms.

FIG. 2 is an exploded isometric view of a rifle-length buffer assemblyin accordance with embodiments of the present invention.

FIG. 3 is a view of the front end of a buffer assembly in accordancewith the embodiment of FIG. 2.

FIG. 4 is a cross sectional view of a buffer assembly as seen at sectionA-A of FIG. 3.

FIGS. 5-10 are front end and cross sectional views of the bufferassembly of FIGS. 3-4 as seen at various times during the bufferretraction cycle.

FIGS. 11-15 are various side and end views of a buffer in accordancewith embodiments of the present invention.

FIGS. 16-17 are isometric views of a buffer in accordance with theembodiment of FIGS. 11-15.

FIG. 18 is an exploded isometric view of a buffer in accordance with theembodiment of FIGS. 11-15.

FIGS. 19-22 various side and end views of a damper post in accordancewith embodiments of the present invention.

FIGS. 23-24 are isometric views of a damper post in accordance with theembodiment of FIGS. 19-22.

FIG. 25 is an exploded isometric view of a damper post in accordancewith the embodiment of FIGS. 19-22.

FIG. 26 is an exploded isometric view of a carbine-length bufferassembly in accordance with embodiments of the present invention.

FIG. 27 is a view of the front end of a buffer assembly in accordancewith the embodiment of FIG. 26.

FIG. 28 is a cross sectional view of a buffer assembly as seen atsection B-B of FIG. 27.

FIGS. 29-34 are front end and cross sectional views of the bufferassembly of FIGS. 3-4 as seen at various times during the bufferretraction cycle.

FIG. 35 is an exploded isometric view of a damper disc in accordancewith embodiments of the present invention.

FIGS. 36-37 are isometric views of a damper disc in accordance with theembodiment of FIG. 35.

FIGS. 38-40 are various side and end views of a damper post inaccordance with the embodiment of FIG. 35.

FIG. 41 is an isometric view of a buffer assembly in accordance withembodiments of the present invention as positioned in connection with alower receiver.

DETAILED DESCRIPTION

Throughout this application, the directional references, such asforward, rearward, left, right, bottom and top, will be used. These andother such references are relative to the firing direction of thefirearm, which fires in a forward direction. Such references are usedfor ease in describing the present invention and should not be construedas limiting the scope of the invention. As used in the descriptionherein and throughout the claims, the following terms take the meaningsexplicitly associated herein, unless the context clearly dictatesotherwise: the meaning of “a,” “an,” and “the” includes pluralreference, the meaning of “in” includes “in” and “on.” Also, referencedesignators shown herein in parenthesis indicate components shown in afigure other than the one being discussed.

FIG. 1 shows an embodiment a prior art carbine buffer assembly used withthe AR15/M16 family of firearms. The buffer assembly 100 includes acarbine length buffer tube (also known as a receiver extension) 130,spring 140, bolt carrier 104, bolt 106 and buffer 120. The rear end ofthe bolt carrier 310 abuts the front of the buffer 320 when the hostrifle is fully assembled. The buffer 120 is contained within the buffertube 130 and the bolt carrier 104 within an upper receiver when inbattery. While the carbine buffer tube 130 does not receive the entirelength of the bolt carrier 104 during its reciprocating motion, thelength of the buffer tube is required to facilitate sufficient rearwardmovement of the bolt carrier 104 and compression of the spring 140 forproper function of the firearm. The spring 140 and buffer 120 arerequired to provide a surface and force that resists the rearwardmovement of the bolt carrier 104. The weight of the buffer 120 maybeselected to minimize bolt bounce and assist in the proper operation of agas operating system.

In existing buffer assemblies, the buffer has mass, the inertia of whichmust be overcome by the building forces within the operating system ofthe rifle. This imparts a desired delay in the cycle of the mechanism.The buffer contains weights that can be changed out for more or lessdesired weight, depending on the mass required for the correct operationof any number of specific weapon configurations. These weights are madefrom steel rod, with an oxide finish. The steel weights may be separatedby rubber disks intended to dampen impact and noise. The steel oxidefinish and rubber disks create significant friction and resistance tofree motion.

The weights inside the buffer are allowed to move fore and aftapproximately 0.080″ to delay the impact force of the buffer body atboth extremes of its travel. The purpose of the free weight inside thebuffer is to create a “double blow” or a delayed impact to hold thebuffer unit stationary for a moment at each end of its travel cycle.This delay is required to allow time for the magazine to present acartridge into the path of the reciprocating bolt, and at the “battery”position, to hold the bolt closed- to prevent a condition called “boltbounce” that can halt normal firing function.

The body diameter of the buffer is significantly smaller than the insidedimension of the buffer spring, and the diameter of the spring issignificantly smaller than the inside diameter of the receiverextension, to allow for variation in manufacturing and also tofacilitate assembly or disassembly. The buffer body is traditionallymade from aluminum and anodized.

The disparities in interfacing dimensions create compound coiling as thespring compresses. This action creates excessive noise and friction; asthe spring compresses and takes on a secondary spiral it grows andcreates a braking force against the walls of the receiver extension.This increasing side load and friction contributes to inconsistentcyclic timing and ultimately sporadic malfunction. Prior bufferassemblies have significant differences between buffer body and springinside diameter, the spring outside diameter and receiver extensioninside diameter, and the buffer “head” outside diameter and receiverextension inside diameter. These differences in these dimensionsgenerally exceed 0.030 inches. These large tolerances contribute tonoise, friction, binding, wear, and rough operation.

The buffer head 122, where it contacts the rear face of the bolt carrier104, is a smooth flat surface. These two parts are allowed to shift outof alignment in any direction; further increasing the potential andfrequency that the carrier may rub or contact the inside surface of thereceiver extension. As the carrier is allowed to pitch and yaw,increased wear will result inside the upper receiver.

Each of these incidences of friction, and/or misalignment can combine tocreate a compounded effect that results in a rifle with rough, noisy,and inconsistent and ultimately unreliable operation. This incrementaldecay of the integrity of the system will lead to poor accuracy, anddiminished service life of the firearm. In addition, the spring isconsidered a wear item that needs routine and regular replacement.

Accordingly, there exists a need for a buffer assembly that is lighter,quieter, smoother, and easier to tune and adjust to meet individualrequirements. Advantages of such an improved buffer assembly may includeenhanced performance and capability to the shooter. Accuracy, speed,control, and recovery between shots may also be positively affected.

FIGS. 2-4 shows a buffer assembly 200 in accordance with embodiments ofthe present invention. The buffer assembly 200 includes a receiverextension 230 (also referred to as a buffer tube). The receiverextension 230 is generally tubular in shape with a rear end 232 and anopen front end 234. The rear end 232 may include a reduced diameter suchthat a shoulder 233 is formed or may be closed. The front end mayinclude a threaded outside diameter 235 that is adapted to engage athreaded inside diameter of the lower receiver of a firearm. Thereceiver extension 230 illustrated in FIG. 2 has a length appropriatefor a rifle configuration of a firearm such as an AR-15.

Embodiments of the buffer assembly 200 further comprise a liner 250. Theliner 250 may comprise a thermoplastic polymer, for example PET(polyethylene terephthalate) or PETG (PET glycol-modified).Alternatively, the liner 250 may comprise another appropriate materialas would be understood by one of ordinary skill in the art, includingPTFE (polytetrafluoroethylene), phenolics, nylon, acetal, UHMWPE(ultrahigh-molecular-weight polyethylene) or other materials. Inembodiments of the invention it is advantageous to use a material thatreduces the friction of the internal components against the interiorsidewall 236 of the receiver extension. In some embodiments, the linermay have a thickness of between 0.010 and 0.020 inches and morepreferably between 0.015 and 0.018 inches.

The liner 250 may, as shown in FIGS. 2-4, be formed from a sheet ofmaterial that is rolled into a tubular shape and inserted into the boreof the receiver extension such that a seam 252 extends longitudinallyalong a side of the bore. Alternatively, the liner may be formed in as atube or may be sprayed or otherwise applied to an interior sidewall 236of the extension 230.

Embodiments of the buffer assembly 200 further comprise a spring 260. Inthe illustrative embodiment, the spring is a coil spring. The liner 250is positioned between an interior sidewall of the receiver extension 230and an outside diameter of the spring 260. Among other advantages, theliner reduces friction between the spring and the receiver extensionsidewall. The internal diameter of the liner 250 is very close to theoutside diameter of the spring 260. In some embodiments, the differencebetween outside diameter of the spring and the inside diameter of theliner is 0.030 inches or less across the diameter, and preferably lessthan 0.010 inches across the diameter.

Embodiments of the buffer assembly may be used in any AR-15 patternedrifle. In carbine applications (short stock), a standard spring intendedfor the AR-10 carbine may used. In rifle applications (fixed, longstock), an AR-10 rifle spring or an AR-15 rifle spring may be used. Thespring rate may be chosen as would be understood by one of ordinaryskill in the art. Higher rate springs may have an increase rate ofdeceleration, which contributes to decreased felt recoil, and a morepositive forward stroke of the system.

Embodiments of the buffer assembly 200 also comprise a buffer 300. Thebuffer is shown in more detail in FIGS. 11-18. The buffer may include abuffer body 320 and a buffer head 322. The buffer body includes areduced diameter nose portion 324 at a rear end of the buffer body, agenerally cylindrical central portion 326, and a bearing surface orguide ring 328 at a forward end of the buffer body 320. The guide ring328 has a larger diameter than the central portion 326, forming ashoulder 330 where the two sections meet. The guide ring 328 isgenerally cylindrical, but may have one or more flat or concave portions332 formed at intervals around its circumference. The guide ring may actas a bearing surface between the buffer body 320 and an interior surfaceof the receiver extension 230 or liner 250.

The buffer body 320 also includes a generally cylindrical cavity 334that extends longitudinally into the buffer body from the forward end.The buffer body also includes air passageways 336, 338 extending throughthe sidewall of the buffer body near the forward and rearward ends. Thebuffer body 320 may be formed of any appropriate material, but ispreferably formed from a polymer, for example a PET.

The buffer head 322 is removably connected to the buffer body 320 toenclose the cavity 334. The buffer head may comprise a bumper 340. Thebumper 340 may be connected to the buffer head 322 by pressing a post342 formed on a forward portion of the bumper into a hole 344 extendingthrough the buffer head. The buffer head main portion 346 may be formedof aluminum, and in particular, a relatively hard aluminum (2xxx or 7xxxseries). The bumper 340 may be formed of a polymer. In particular, thebumper 340 may be a relatively hard polymer damper for mitigating impactforces caused by the impact of the buffer weight(s) (discussed below) asthe system returns to battery at its forward position.

The buffer head may serve as a bearing surface for the hardened steelbolt carrier (104). The forward surface of the head (that which contactsthe carrier) is shaped as a truncated cone 348, sufficient to interactwith the bolt carrier on the datum of the cone. Engagement between thebolt carrier and the cone 348 helps ensure proper coaxial andperpendicular alignment of the bolt carrier group and the bufferassembly. This measure ensures the bolt experiences no tilt or pitch,which can contribute to poor function and excessive wear.

This guide ring 328 of the buffer body 320 has larger diameter than thehead 322 to prevent the head from contacting the receiver extensionsidewall 236. Accordingly, in some embodiments, the polymer guide ring328 my contact the sidewall 236, but the aluminum buffer head 322 willnot.

When the buffer 300 is inserted into the receiver extension 230, thespring 260 surrounds the nose 324 and central portion 326 of the bufferbody 320. An end of the spring seats against a shoulder 330 formedbetween the central portion 326 and guide ring 328 of the buffer body.The outside diameter of the buffer body central section 326 is veryclose to the inner diameter of the spring 260. In some embodiments, thedifference between inside diameter of the spring and the outsidediameter of the buffer body is 0.030 inches or less across the diameter,and preferably less than 0.010 inches across the diameter.

The Buffer 300 may also comprise one or more weights 350. The weight 350is inserted into the cavity 334 of the buffer body 320. In someembodiments, the weight has a generally cylindrical shape that coincideswith the shape of the cavity. However, the weight is shorter than thecavity 334 so that the weight 350 can reciprocate within the cavity. Theweight may be polished to reduce friction and ease movement within thecavity, particularly if the buffer body is constructed of a polymermaterial.

The weight 350 may include a single weight or multiple weights invarious configurations. The total mass inside the buffer body may bealtered by substituting different materials and/or structures. Weightexamples include tungsten, steel, or aluminum, formed into bars orpellets or balls, or steel or lead or tungsten granulated media. Othersuitable materials include brass, nickel, carbide, copper, zinc, oralloys such as Babbitt or Mallory. Adjusting the buffered mass insidethe buffer body may allow a user to fine tune the system's timing andthe energy imparted by the buffer to balance recoil forces of the rifle.

As illustrated in FIG. 41, the buffer head 322 is easily removable,while the rest of the system remains inside the rifle. This way, theoperator may make changes to the buffer mass without requiring tools orcleaning supplies. The user is not required to remove the greased orotherwise chemically treated components from the rifle. In embodimentsof the present invention, the buffer head 322 is not otherwise affixedto the buffer body 320; it is maintained between the carrier (104) andbuffer body 320 by the buffer spring 260 tension. When the rifle is“opened” to allow cleaning or maintenance, the buffer retainer 352 isresponsible for keeping the buffer head contained.

Returning to FIGS. 2-4, embodiments of the buffer assembly 200 furthercomprise a damper assembly 400. The damper assembly 400 is shown in moredetail in FIGS. 19-25. The damper assembly 400 is positioned adjacentthe rear end of the receiver extension 230. The assembly comprises adamper post 410 and a damper ball 430. The damper post 410 comprises acentral section 412 with a generally cylindrical shape. The damper postfurther comprises a nose section 414 having a reduced diameter at aforward end of the damper post and a head section 416 at a rearward endof the damper post. The head 416 has a diameter that is larger than thediameter of the central section 412. The damper post 410 extends forforward from the rear end of the receiver extension, thereby spacing thenose portion 414 some distance from a rear end of the receiverextension. Preferably, the spaced distance is greater than the diameterof the receiver extension bore 234 for rifle embodiments illustrated inFIGS. 2-4. The length of the post 410 may act as a guide rod to maintaincontrol of the spring 260 as it compresses and extends.

The damper post head 416 has a larger diameter than the central portion412, forming a shoulder 418 where the two sections meet. When the damperassembly 400 and the spring 260 are inserted into the receiver extension230, the spring 260 surrounds the nose 414 and central portion 412 ofthe damper post 410. An end of the spring seats against a shoulder 418formed between the central portion 412 and head 416 of the post. Theoutside diameter of the damper post central section 412 is very close tothe inner diameter of the spring 260. In some embodiments, thedifference between inside diameter of the spring and the outsidediameter of the damper post is 0.030 inches or less across the diameter,and preferably less than 0.010 inches across the diameter.

Embodiments of the damper post 416 include a cavity 420 or recess formedwithin the nose portion 414. In the illustrative embodiments, the cavity420 is centered in the post, generally cylindrically shaped, and extendsto a depth that is less than its diameter.

The damper assembly further comprises a damper ball 430. The damper ballmay be formed, at least in part, from a fluoropolymer material, forexample, Viton® from DuPont, that absorbs and dissipates energy andimpact forces. Other materials may be used as would be understood by oneof skill in the art. However, it is preferable that the material thatreduces return energy and rebound impact forces. A rapid return ofenergy in the system may negatively attenuate the intended effect of thebuffer. The energy absorbing nature of a fluoropolymer material, forexample, leaves the buffer spring solely responsible for initiating thereturn stroke of the system.

The damper ball 430 may be positioned in a cavity 420 formed in aforward end of the damper post 410. The damper ball may be sized suchthat it is press-fit into and retained by the cavity. Alternatively, thedamper ball may be adhered or otherwise fixed to the post. The damperball is described and illustrated as a ball having a generally sphericalshape. However, the damper ball may be of any appropriate shape,including, for example, a cylinder, a hemisphere, a disc, a cube or anyother shape that would allow it to extend beyond the end of the damperpost 410.

FIGS. 5-10 illustrate the recoil stroke of the buffer assembly 200. FIG.6 shows the buffer assembly in fully forward position, for example whenthe bolt of the firearm is closed at the beginning of the firing portionof the firearm's cycle. As the bolt (106) and bolt carrier (104) of thefirearm begin to move backward, the buffer 300 is driven backward withinthe bore 234 of the receiver extension 230. At the end of the rearwardstroke, the nose portion 324 of the buffer body 320 contacts the damperball 430 attached to a forward end of the damper post 410. The movementof the buffer 300 causes the weight 350 to move back and forth withinthe buffer body cavity 334.

FIGS. 26-28 shows a buffer assembly 1200 in accordance with embodimentsof the present invention. The buffer assembly 1200 is generally similarto the buffer assembly embodiments shown in FIGS. 2-4 except that it isadapted for use with a carbine configuration of a firearm. Accordingly,the receiver extension 1230 illustrated in FIG. 26 has a lengthappropriate for a carbine configuration of a firearm such as an AR-15.In addition, the damper post (410) of the rifle configuration isreplaced with a damper disc 510.

Embodiments of the buffer assembly 1200 comprise a damper assembly 500.The damper assembly 500 is shown in more detail in FIGS. 35-40. Thedamper assembly 500 is positioned adjacent the rear end of the receiverextension 1230. The assembly comprises a damper disc 510 and a damperball 430. The damper disc 510 comprises a central section 512 with agenerally cylindrical shape. The damper disc further comprises a nosesection 514 having a reduced diameter at a forward end of the damperdisc and a head section 516 at a rearward end of the damper disc. Thehead 516 has a diameter that is larger than the diameter of the centralsection 512.

The damper assembly 500 further comprises a damper ball 430 as describedabove. In contrast to the damper post (410) of the rifle configuration,the damper disc 510 does not space the damper ball 430 away from therear wall of the receiver bore 234. Rather, the damper disc may comprisea cavity 520 formed in the nose portion 514 that extends through asignificant portion of the length of the damper disc. In someembodiments, the cavity extends completely through the damper disc suchthat an opening 522 is formed on the rear side of the damper disc. Thedamper ball 430 may be positioned in a cavity 520 formed in the damperdisc 510.

Illustrative embodiments of the invention show the use of a damper post(410) or a damper disc (510). However, one of skill in the art wouldunderstand that the damper post/disc is not limited to the specificallyillustrated lengths and that a post/disc of any length in between may beappropriate depending on the length and configuration of the firearm'sstock and receiver extension.

The damper disc head 516 has a larger diameter than the central portion512, forming a shoulder 518 where the two sections meet. When the damperassembly 500 and the spring 260 are inserted into the receiver extension1230, the spring 260 surrounds the nose 514 and central portion 512 ofthe damper disc 510. An end of the spring seats against a shoulder 518formed between the central portion 512 and head 516 of the disc. Theoutside diameter of the damper disc central section 512 is very close tothe inner diameter of the spring 260. In some embodiments, thedifference between inside diameter of the spring and the outsidediameter of the damper disc is 0.030 inches or less across the diameter,and preferably less than 0.010 inches across the diameter.

FIGS. 29-34 illustrate the recoil stroke of the buffer assembly 1200similar to that shown in FIGS. 5-10.

We claim:
 1. A buffer assembly for a firearm compromising: a receiverextension having a tubular shape, the receiver extension comprising arear end, an open front end, an inner surface and an outer surface; adamper assembly positioned within the receiver extension adjacent thereceiver extension rear end; a spring positioned within the receiverextension, wherein the spring comprises an outer surface, a front endand a rear end, wherein and the spring rear end at least partiallysurrounds the damper assembly; a buffer positioned within the receiverextension, wherein the buffer comprises a weight and the spring frontend at least partially surrounds the buffer; a liner at least partiallycovering the inner surface of the receiver extension, wherein the lineris positioned between at least a portion of the spring outer surface anda portion of the receiver extension inner surface.
 2. The bufferassembly of claim 1 wherein the buffer further comprises a buffer bodyand a buffer head.
 3. The buffer assembly of claim 2 wherein the bufferbody comprises a cavity and the weight is positioned within the bufferbody cavity.
 4. The buffer assembly of claim 3 wherein the buffer bodycavity comprises an open end and the buffer head is removably connectedto the buffer body to enclose the cavity.
 5. The buffer assembly ofclaim 2 wherein the buffer body comprises a polymer material.
 6. Thebuffer assembly of claim 2 wherein the buffer head comprises aluminum.7. The buffer assembly of claim 1 wherein the spring comprises a coilspring having an inside diameter and an outside diameter.
 8. The bufferassembly of claim 7 wherein the damper assembly comprises a damper post.9. The buffer assembly of claim 8 wherein the damper post comprises ahead section, a central section having an outside diameter and a nosesection.
 10. The buffer assembly of claim 9 wherein a difference betweenthe inside diameter of the spring and the outside diameter of the damperpost central section is 0.030 inches or less across the diameter. 11.The buffer assembly of claim 9 wherein a difference between the insidediameter of the spring and the outside diameter of the damper postcentral section is less than 0.010 inches across the diameter.
 12. Thebuffer assembly of claim 1 wherein the damper assembly comprises adamper ball.
 13. The buffer assembly of claim 1 wherein the linercomprises a thermoplastic polymer.
 14. The buffer assembly of claim 1wherein the liner has a thickness of between 0.010 and 0.020 inches. 15.The buffer assembly of claim 1 wherein the liner has a thickness ofbetween 0.015 and 0.018 inches.
 16. The buffer assembly of claim 1wherein the liner comprises a sheet of material rolled into a tubularshape and inserted into the receiver extension such that a seam extendslongitudinally along a side of the receiver extension inner surface. 17.The buffer assembly of claim 1 wherein the liner comprises a tube. 18.The buffer assembly of claim 1 wherein the liner comprises a materialthat is sprayed onto the receiver extension inner surface.
 19. Thebuffer assembly of claim 7 wherein a difference between the outsidediameter of the spring and an inside diameter of the liner is 0.030inches or less across the diameter.
 20. The buffer assembly of claim 7wherein a difference between the outside diameter of the spring and aninside diameter of the liner is less than 0.010 inches across thediameter.